Diffusion mechanism in aluminum–silicon structures surface-irradiated by off-electrode plasma of a high-voltage gas discharge

The mechanism of diffusion in Al–Si structures that arises during surface irradiation by off-electrode plasma of a high-voltage gas discharge (discharge current and voltage are $I$ = 50 mA and $V$ = 4 kV, irradiation time varies from 90 to 600 s) has been investigated. A model to calculate the aluminum impurity concentration distribution in a silicon wafer versus irradiation parameters has been suggested. Analytical relationships that are in good agreement with the experiment have been derived. It has been shown that the aluminum diffusion coefficient in the semiconductor is maximal at the electron penetration depth owing to electron-induced vacancies arising in a $\sim$0.25-$\mu$m-thick layer. As a result, the thermal diffusion coefficient rises by two to three orders.